Inventive concepts relate to semiconductor memory devices, and more particularly, to nonvolatile memory devices.
A semiconductor memory device is a memory device in which data can be stored and the stored data can be read whenever desired. The semiconductor memory device is classified as a volatile memory device or a nonvolatile memory device. When not powered, a volatile memory device loses stored data. Examples of the volatile memory device include a static random access memory (SRAM), a dynamic random access memory (DRAM), and a synchronous dynamic random access memory (SDRAM). A nonvolatile memory device retains the stored data even when not powered. Examples of a nonvolatile memory device include a read only memory (ROM), a programmable read only memory (PROM), an erasable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM), a flash memory device, a phase-change random access memory (PRAM), a magnetoresistive random access memory (MRAM), a resistive random access memory (RRAM), and a ferroelectric random access memory (FRAM). The flash memory device is classified into a NOR type or a NAND type.